hi guys im trying to have the worst contribution possible on this sit Is It RaTeD?Is It RaTeD?Is It RaTeD?Is It RaTeD?Is It RaTeD?Is It RaTeD?Is It RaTeD?Is It RaTeD?Is It RaTeD?Is It RaTeD?Is It RaTeD?Is It RaTeD?Is It RaTeD?Is It RaTeD?Is It RaTeD?Is It RaTeD?Is It RaTeD?Is It RaTeD?Is It RaTeD?Is It RaTeD?Is It RaTeD?

OH, I was wondering why my code did not work. Because I wrote it completely based on picture. That is annoying -_- EDIT: Picture is not wrong, but without clarification I did something else/not what the problem wanted.

What the hell is happening? A lot of problem with problem statement. "You can remove no digits (that is, leave it as is)." This cost me 5 WA. Important information of problem C is given after 1:30 hr "You should do exactly one rotation of cube" "There was an issue with picture in notes for problem C, now it's fixed" . Is it a joke?

Well, your point is a bit orthogonal, as knowing algorithms is directly related to CP. However, I think the author isn't wrong to include a problem on something as well known as rubiks cube. In the past we had problems about Matryoshka dolls too.

Many problems to be pointed out there, including unclear statements (at least in English, I'm not sure about the original ones) or extremely scarce range of pretests (I even received "Pretest passed" for problem B even though I misunderstood the problem statement, and well, of course, it got hacked later xD) Hope your next contest would be better.

I'm getting so sick of CF rounds. It seems every time I participate something goes wrong, either during contest or during systest. Every other round is unrated, problems are mostly unimaginative and I wonder why I should devote 2h of my day for such contests. Today's round was another hack round, no knowledge required to be in top20 (just a bad enough room). A's most obvious 'corner case' should've been in the pretests. All C solutions I saw while hacking were hideous, and if the solution was "check all possibilities", it's really bad. This rounds issue wasn't D, it was the whole round. (this comment doesn't concern E and F since I haven't tried them, but just looking at the number of ACs, it seems too hard for a div2 round).

If you're getting sick, better not compete here anymore, you absolutely don't have to. If you do, you'd better accept that mistakes can be made and respect the effort of the authors. Or don't listen to my advice and be sour... |-)

This is not about this particular contest or author (even thought in my earlier frustration it might have sounded differently), it's about how often it is, and that I can rarely just compete uninterrupted on this platform. There is a saying "We critique the things we love, so they could be even better", I love CF and its community and I want it to do good, I was just voicing my frustrations.

There are 3 possibilities: 1. They solved these problems based on their own knowledge (about rubiks, cubes, or something similar) 2. They took a guess. Like in Problem C, we could guess the order of the color no. based on the diagrams. 3. If things got too dicey, you can ask the jury. Remember that feature, you'll need it, perhaps even in a real contest.

I had to read twice to see whether zero rotations would be allowed, but was able to conclude from the problem statement that it was not. The announcement was not necessary. And in my opinion proper reading is part of the challenge.

Yes I agree with you that proper reading is part of the challenge. But how can you understand it is valid to delete no digit form this statement "Her problem is following: for given string, consisting of only 0 and 1, tell if it's possible to remove some digits in such a way, that remaining number is a representation of some positive integer, divisible by 64, in the binary numerical system." ? Is (some==none) gives you a 1 ?

In your comment "I had to read twice to see whether zero rotations would be allowed, but was able to conclude from the problem statement that it was not. The announcement was not necessary." This portion is about problem C.

And "And in my opinion proper reading is part of the challenge." this portion is universal as it is your opinion. Generally opinions are global unless you write them in problem C(cube) scope { }.

If I correctly understand what you do: A) There are two more sequences for "temp": 3 4 17 19 10 9 16 14 and 1 2 18 20 12 11 15 13. B) Your sequences in "temp" are disordered: for example, the first shoud be 1 3 5 7 9 11 24 22. C) You fill "t" wrong: you should move 7 to 1, 6 to 0, and so on.

Yes, it's unrated and I appologise for it and will try my best to make this never happen again. Despite it, hope you liked the problems.

Problem preparation is a very hard process and it's quite easy to make a mistake there. Hopefully, Polygon platform was designed and it helps to find most of errors automaticly. Moreover, before any Codeforces round some people solves it before beginning to make sure that everything is all right. In most cases it's enough to make sure that there are no mistakes there, but today it wasn't enough. Error in stament of problem D today was done during rewriting statemnts from drafts, which happened too late, so most of the testers read correct draft of statement, but not the final version with mistake. Of course, many people read final version of statement before beginning, but nobody noticed that something changed between these two versions.

Of course it was a good lesson, and I will try to be much more careful next time.

While posting the editorial, I will REALLY appreciate if you guys can help us grasp an elegant way to do problem C (rubick's cube) for this round. My code was all mess (and failed pretest 7 XD) and it boiled down to me not able to implement it elegantly. I will be grateful if that can be considered! Thanks :)

Here is my idea that I think is right but couldn't implement correctly during contest:

Lets start by compressing the heights of the models. Then go over each model and find the first and second models to the right of him(I will call them nxt[1] and nxt[2]) that are shorter than him ( you can do this with segment tree). After we do this lets call every model i whose (next[1] — i) > k "bad". Now its clear we must do a swap with a left model that is atmost K models to the right of every "bad" model. After that, I give every model a lower bound and an upper bound of the height of the model he will be swapped with:

lower bound — min(a[i+1],a[i+2] ..... a[i+k])

upper bound — min( every model that has model i as his nxt[1] and nxt[2] — that model is > k)

After having both of these things. I go over every potential left model and find if there is intersection between him and some lower and upper bound. If there is, the answer is yes otherwise its no

nxt[i][2] is the second index to the right of the model i that is shorter than him, right?

since we are swapping the nxt[i][1] of that model with someone else, we must rely on nxt[i][2] now. If the distance between i and nxt[i][2] is more than k we must rely on the model we are swapping nxt[i][1] with, and giving it an upper bound( since the model we swap it with will have to be shorter than all models that will rely on him)

My WA was that I forgot when we swap the left model must be taller than the right one. And also sorry for the messy code, too much pressure in the last 15 minutes :D. If you have questions regarding the code feel free to message me.

A — the leftmost position of model who violates the beauty (a lower model is more than k positions to the right).

We must swap the higher model with lower on position A+k — I think I am able to sort of justify/prove that — if it is not possible, NO.

Look for the biggest value lower than a[A] to the right and take the leftmost such value — I can't prove/justify that so it might be wrong. Just wrote couple of examples which showed that it was working and could not find a counterexample — call this pos.

If there is no pos -> NO.

Swap a[A+k] with a[pos] and verify that everything looks good -> YES or NO.

I've never been to Div. 1. I have tried, I have come close, but I couldn't. And then today, I performed well at last. Well, maybe the hacks were the main boost today, but still, it's a part of CF, right? And I was happy that at last today I'll be in Div. 1. And then, it was unrated. I know many of you have faced this, but still, it hurts...a lot!!! I just don't know what to say. Guys, before arranging a round, please be careful :( I don't know if I should be angry or sad or frustrated. I know you guys will say, "you will get more chances" and all, and "if you are a good coder then this shouldn't bother you, you'll (should) be in Div. 1 without this", but still, it's painful AF!

Well problems E and F were nice. I didn't look at A, B, C and D but the last two problems were much better than in a lot of div.2 rounds — in a lot of div.2 rounds last 1/2 problems are just obvious. In this round the last two problems didn't have an obvious solution at all. So it's wrong judging a round by just the first couple of problems. IMO the contest was nice and I don't see why the round is hated so much.

It's the very strange position. Why do you forget that this round is definetely not for you? What can do a usual Codeforces Div2 member? Do you really think that they won't hate it, when they had the E and F problems which they knowingly couldn't solve just because they hadn't skill like you, the D problem which was wrong and the C problem which supposed a stupid realization? And what can I say to my pupils? When I will say: "You need to solve Codeforces contests because it's very beneficial for your skill", how will they believe me when they spent 2,5 hours of their time senselessly and they were deprived pleasure?

The goal of the contest should be 'improving problem solving skills' and not just 'improving ratings'. Problem setters must have cross checked all the problem properly because this type of things disappoint a lot, but they are also human and they are allowed to make mistakes.

Statements has changed after testing, that's why nobody noticed mistakes in statements. Of course, changing statements after testing is a bad idea. I hope this situation will never happen again, at least until the coordinator of rounds changes.

Btw I can't agree that Denisson 's one is more notorious than nssprogrammer 's one. (-688 votes on comment < -483 votes on blog). This is his first contest on codeforces, and actually plagiarism is one of the worst thing in the prograamming contest.

This is not plagiarism, or not the worst thing (Half of problems are not bad), so I think the weight of indiscretion is not larger than nssprogrammer 's "Notorious Coincidence".

Here the problem is not whether contest is rated or not,but what matters is time.here most of people who are participating after leaving some important work e.g. that time which I should be devoting to prepare for exams, sacrificing the midnight sleep, some may be having a very tight schedule after job, and they are doing contests instead of relaxing and spending time with family. In such a scenario, It definitely hurts if u have to spend 2hrs unproductively.

But it means you should care about risk of this. If I encountered in the same pattern I would think that "it's unrated, but it's just a coincidence. I should think about the possiblilty of unrated (note that it doesn't mean I will ask whether the contest is rated or not)". That's one of what programming contest stand for, I think.

First of all, 64 = 1 000 000 We need to find position of the first '1' at the string, then just calculate the count of zeros between pos and length of string. If we can make 1 000 000, then the answer is "yes"

Wow, I noticed that the problem A, C, D (problem which the factor of downvotes) was made by ayoyia, not Denisson, by seeing editorial. I think his responsibility is light and should not get too much downvotes.